"A SMALL-SIZED VEHICLE ON WHICH IS MOUNTED AN INTERNAL COMBUSTION ENGINE"

Abstract

A small-sized vehicle on which is mounted an internal combustion engine including a crankcase in the rear, a cylinder block attached in front of the crankcase, a cylinder head attached in front of the cylinder block, and a cylinder head cover attached in front of the cylinder head, wherein the cylinder block has a cylinder with its axis tilted to extend so as to be higher in the forward direction of the vehicle, wherein a heat exchanger as a lubricating oil cooling device is provided closely to the engine, and wherein the cylinder block has internal lubricating oil passages, characterized in that: said cylinder block has an oil inlet opening and an oil outlet opening for the internal lubricating oil passages of the cylinder block; a first joint pipe connects said oil outlet opening of the cylinder block to an oil inlet joint pipe provided on the heat exchanger and a second joint pipe connects an oil outlet joint pipe provided on the heat exchanger to said oil inlet opening of the cylinder block.

Full Text

The present invention relates to a small-sized vehicle on which is mounted an internal combustion engine.
TECHNICAL FIELD
[0001]
The present invention relates to a vehicle-mounted internal combustion engine with a lubricating oil cooling device.
BACKGROUND ART [0002]
There is known a vehicle-mounted internal combustion engine wherein a lubricating oil heat exchanger is disposed in close proximity to the front of the internal combustion engine mounted on a motorcycle (see, for example. Patent Document 1).
Patent Document 1: JP 57-183509 A [0003]
The internal combustion engine disclosed in Patent Document 1 is an internal combustion engine in a V-arrangement with cylinders thereof obliquely erected in front and rear banks. The heat exchanger, which is a lubricant oil cooler, is disposed closely and forwardly
of a crankcase of the engine, and oil pipes extending from the heat exchanger are connected to openings of a lubricating oil passage in the crankcase, which are formed in the side wall of the crankcase. [0004]
There is known another arrangement in which a heat exchanger as a lubricant oil cooler is disposed forwardly of a front cylinder bank of an engine with tilted cylinders, and pipes extending from the oil cooler are connected to openings in a cylinder head of the engine (see, for example. Patent Document 2). [0005]
Patent Document 2: JP 9-240545 A DISCLOSURE OF THE INVENTION
Underlying Problem to be solved by the Invention [0006]
The internal combustion engine disclosed in Patent Document 1 is of the V-shaped type, when seen from the side, with the front cylinders not tilted at a large angle in the forward direction of the vehicle body. Therefore, the heat exchanger as the lubricant oil cooler can be disposed closely and forwardly of the crankcase, and the oil pipes extending from the heat exchanger to the crankcase need not be long. However, if the cylinders
are tilted at a large angle in the forward direction of the vehicle body, the heat exchanger will have to be positioned further forwardly of the cylinder head so that the heat exchanger will be spaced largely from the crankcase, resulting in an increase in the length of the lubricant oil pipes. If the pipes are long, then it causes a large oil pressure loss, resulting in a need to increase the capacity of the lubricant oil pump, etc. [0007]
With the internal combustion engine disclosed in Patent Document 2, the pipes interconnecting the oil cooler, as the heat exchanger, disposed forwardly of the front cylinder bank and the openings in the cylinder head are extremely short. This causes a limitation to the layout of the lubricant oil cooler, while if a desired layout should be achieved, then pipes which need to be longer than necessary have to be employed, which incurs an increase in the manufacturing costs. [0008]
The present invention has been made in view of the above shortcomings. It is an object of the present invention to provide a vehicle-mounted internal combustion engine for small vehicles, with a lubricating oil cooling device, which can employ an optimum length of
the pipes to achieve a desired freedom of layout for the heat exchanger as lubricant oil cooler and to avoid increase in the manufacturing costs. Means for solving the Underlying Problem [0009]
To achieve the above object, in accordance with the present invention, there is provided a vehicle-mounted internal combustion engine with a lubricating oil cooling device, which engine is mounted on a small-size vehicle with a cylinder thereof forwardly tilted at a large angle, characterized in that: a heat exchanger as the lubricating oil cooling device is disposed closely and either forwardly or rearwardly of the internal combustion engine; lubricating oil passages formed in a cylinder block of the internal combustion engine has openings in the cylinder block; and pipes extending from the heat exchanger are connected to the openings in the cylinder block. [0010]
The heat exchanger may be fixed to a vehicle body frame, for exaple, to downpipes provided on the vehicle. [0011]
Preferably, the heat exchanger is in the shape of a flat rectangular parallelepiped and has a flat surface
directed in a forward direction. Preferably, the flat
surface is directed obliquely upwards.
[0012]
Preferably, the pipes are connected to a side surface of the heat exchanger and to a side surface of said cylinder block. [0013]
Typically, a cylinder head is provided forwardly of the cylinder block and the heat exchanger is disposed forwardly of the cylinder head. Effect of the Invention [0014]
Since the pipes extending from the heat exchanger, which is disposed closely and either forwardly or rearwardly of the internal combustion engine with the cylinder tilted forwardly at a large angle, are connected to the openings in the cylinder block, the pipes can have an optimum length, not too short or too long, whereby a desired freedom of layout for the heat exchanger is ensured. [0015]
As the cylinder head can be installed and removed without dismounting the pipes and other parts, the lubricating oil cooling device has improved
maintainability. [0016]
Since the heat exchanger is fixed to the vehicle body frame, for example, to the downpipes at the front of the vehicle, the heat exchanger can be disposed at a certain distance from the internal combustion engine as a heat source, and hence is less susceptible to the heat from the internal combustion engine, whereby the cooling efficiency of the heat exchanger is increased. BRIEF DESCRIPTION OF THE DRAWINGS [0017] [FIG. 1]
FIG. 1 is a side elevational view of an entire motorcycle incorporating a vehicle-mounted internal combustion engine with a lubricating oil cooling device in an embodiment of the present invention. [FIG. 2]
FIG. 2 is an enlarged side elevational view of a principal portion of the motorcycle. [FIG. 3]
FIG. 3 is a front elevational view of the principal portion of the motorcycle. [FIG. 4]
FIG. 4 is a side elevational view of a cylinder
block. [FIG. 5]
FIG. 5 is a view as viewed in the direction indicated by the arrow V in FIG. 4. [FIG. 6]
FIG. 6 is a cross-sectional view taken along line VI - VI of FIG. 4. DESCRIPTION OF REFERENCE SIGNS [0018]
!••'Motorcycle, 2-•'Head pipe, 3-•-Main frame, 4•••Downpipe, 5*•-Center frame, 6'•'Helmet box, 7-•-Fuel tank, 8'•'Seat, 10••'Front fork, 11••'Front wheel, 12••'Rear fork, 13••-Rear wheel, 14••'Rear cushion, 20'•'Power unit, 21••'Internal combustion engine, 22-•-Crankcase, 23'•-Cylinder block, 24••-Cylinder head, 25-•'Cylinder head cover, 26'•'Intake pipe, 27'•'Carburetor, 28'•'Exhaust pipe, 29-•'Muffler, 30'•'Gear mechanism, 40'--Oil cooler, 41a, 42a, 43a-•-Bracket, 41b, 42b, 43b---Stay, 41c, 42c, 43c---Rubber bushing, 45-•-Oil inlet joint pipe, 46-•-Oil outlet joint pipe, 50-••Joint pipe, 51-•-Mounting bracket, 52-•-Mounting flange, 53'••Joint member, 55*••Joint pipe, 56-•'Mounting bracket, 57••-Mounting flange, 58-••Joint member, 60*•-Cylinder liner, 61-•-Chain chamber.
62'•-Stud bolt hole, 63'*0il pressure delivery passage,
63a'•"Oil outlet opening, 64*•'Oil return passage,
64a-•-Oil inlet opening, 66'•-Oil pump, 67'•-Oil suction
passage, 68'•'Oil strainer, 69*•"Oil discharge passage,
70, 71'•-Oil passage
BEST MODES FOR CARRYING OUT THE INVENTION
[0019]
An embodiment of the present invention will be described below with reference to FIGS. 1 through 6. [0020]
FIG. 1 shows a side elevational view of a motorcycle 1 having a vehicle-mounted internal combustion engine with a lubricating oil cooling device according to the present embodiment. [0021]
The motorcycle 1 has a vehicle body frame including a head pipe 2 in a front vehicle body portion. A main frame 3 extends obliquely downwardly and rearwardly from the head pipe 2 and is branched into left and right portions which extend substantially horizontally in a central vehicle body portion and then are bent upwardly as sharply inclined portions, whose upper ends are bent rearwardly into a substantially horizontal rear portion. [0022]
A pair of left and right downpipes 4 and 4 extend downwardly from the main frame 3 near the front end thereof and are then bent rearwardly from bent lower ends 4a and 4a into substantially horizontal portions whose rear ends are connected to the upper main frame portions 3 and 3 through center frames 5 and 5. [0023]
A helmet box 6 is mounted on rear sections of the central horizontal portions of the left and right rear branched main frame portions 3 and 3, and a fuel tank 7 is mounted on rear sections of the main frame portions 3 and 3 behind the helmet box 6. Upper portions of the helmet box 6 and the fuel tank 7 are openably and closably covered with a seat 8. [0024]
A front wheel 11 is supported by a shaft on the lower end of a front fork 10 which is angularly movably supported on the head pipe 2 in the front vehicle body portion. A power unit 20, which includes a unitary assembly of an internal combustion engine 21 and a gear mechanism 30 connected to the a load side of the engine, is supported on the central horizontal portions of the main frames 3 and the center frames 5, and is installed between the main frames 3 and the downpipes 4.
[0025]
A rear wheel 13 is supported by a shaft on the rear end of a rear fork 12 which has a front end pivotally supported on the center frames 5 and extends rearwardly. A rear cushion 14 is interposed between the rear end of the rear fork 12 and the main frames 3 disposed thereabove. [0026]
The internal combustion engine 21 is an air-cooled single-cylinder 4-stroke-cycle engine. The cylinder of the internal combustion engine 21 is tilted to such a degree that the cylinder extends nearly horizontally in the forward direction of the vehicle body. In other words, the cylinder has its axis tilted at a large tilting angle such that the axis extends forwardly of the motorcycle along the portion of the main frame 3 above the cylinder. As shown in Fig.2, the internal combustion engine 21 has a crankcase 22 at the rear thereof. The internal combustion engine 21 has a cylinder block 23 integrally coupled to the crankcase 22, a cylinder head 24, and a cylinder head cover 25, which are arranged in the forward direction in the order named. [0027]
An intake pipe 26 extends upwardly from the
cylinder head 23 which is tilted forwardly in a nearly horizontal attitude, and an exhaust pipe 28 extends downwardly from the cylinder head 23. The intake pipe 26 extending upwardly from the cylinder head 23 is bent forwardly and connected to a carburetor 27, which is connected to an air cleaner (not shown), providing an intake system. The exhaust pipe 28 extending downwardly from the cylinder head 23 is displaced obliquely to the right (to the right side of the motorcycle) and extends rearwardly along a lower right surface of the crankcase 22 into a muffler 29 (Fig.l) which extends rearwardly and slightly upwardly on the right side of the rear wheel 13, providing an exhaust system. [0028]
A lubricant oil cooler (heat exchanger) 40 is disposed forwardly of the cylinder, which is largely tilted forwardly, of the internal combustion engine 21, and positioned in close proximity to the cylinder head cover 25. As indicated in Fig.3, the oil cooler 40 is in the shape of a flat rectangular parallelepiped inclined rearwardly and has an upper end adjacent to the cylinder head cover 25. The oil cooler 40 is sandwiched between the bent portions 4a and 4a of the left and right downpipes 4 and 4 and supported by the downpipes 4 and 4.
The oil cooler 40 in the shape of a flat rectangular parallelepiped has its forward flat surface directed obliquely upward in the advancing direction of the motorcycle. [0029]
Upper and lower brackets 41a and 42a project on the left side of the oil cooler 40, and stays 41b and 42b projecting from the left downpipe 4 are connected to the brackets 4la and 42a through respective rubber bushings 41c and 42c. A bracket 43a projecting on the right side of the oil cooler 40 is connected to a stay 43b projecting from the right downpipe 4 through a rubber bushing 43c. [0030]
In this manner, the oil cooler 40 has its left side connected to the left downpipe 4 through the upper and lower rubber bushings 41c and 42c, and its right side connected to the right downpipe 4 through the rubber bushing 43c, and is supported between the left and right downpipes 4 and 4. [0031]
The oil cooler 40 includes upper and lower tanks oriented laterally and disposed parallel to each other. As shown in Fig.3, an oil inlet joint pipe 45 projects
from the right end of the lower tank, and an oil outlet joint pipe 46 projects from the right end of the upper tank. [0032]
As indicated in Fig.5, the cylinder block 23, which is tilted forwardly at a large tilting angle, of the internal combustion engine 21, has upper and lower oil passage openings 64a and 63a defined in the right side thereof. The lower oil outlet opening 63a is connected by a joint pipe 50 (Fig.2) to the oil inlet joint pipe 45 of the oil cooler 40, and the upper oil inlet opening 64a is connected by a joint pipe 55 (Fig.2) to the oil outlet joint pipe 46 of the oil cooler 40. [0033]
The lower joint pipe 50 includes a flexible pipe 50a and connection pipes 50b, 50c connected to the respective opposite ends of the flexible pipe 50a. A mounting bracket 51 is formed on the distal end of the connection pipe 50b, and a mounting flange 52 is formed adjacent to the distal end of the other connection pipe 50c. [0034]
The distal end of the connection pipe 50b is connected to the lower oil outlet opening 62a, with the
mounting bracket 51 fixed to the right side of the cylinder block 23 with bolts 51a. The distal end of the other connection pipe 50c is connected to the oil inlet joint pipe 45 of the oil cooler 40, and the mounting flange 52 and a joint member 53 on the oil inlet joint pipe 45 are fixed to each other with bolts 52a. [0035]
The joint pipe 50 extending forwardly from the oil outlet opening 62a of the cylinder block 23 passes through the inside space between the downpipes 4 and is connected to the oil inlet joint pipe 45 of the oil cooler 40 for introducing lubricant oil into the oil cooler 40. [0036]
The upper joint pipe 55 includes a flexible pipe 55a and connection pipes 55b and 55c connected to the respective opposite ends of the flexible pipe 55a. A mounting bracket 56 is formed on the distal end of the connection pipe 55b, and a mounting flange 57 is formed adjacent to the distal end of the other connection pipe 55c. [0037]
The distal end of the connection pipe 55b is connected to the upper oil inlet opening 64a, and the
mounting bracket 56 is fixed to the right side of the cylinder block 23 with a bolt 56a. The distal end of the other connection pipe 55c is connected to the oil outlet joint pipe 46 of the oil cooler 40, and the mounting flange 57 and a joint member 58 on the oil outlet joint pipe 46 are fixed to each other with bolts 57a. Therefore, oil returning from the oil cooler 40 passes through the joint pipe 55 back into the cylinder block 23 [0038]
As shown in FIGS. 4 to 6, the cylinder block 23 has fins 23a on its upper, lower and side surfaces and a cylinder liner 60 fitted centrally therein and projecting toward the crankcase 22. A chain chamber 61 (Fig.5) is defined in the cylinder block 23 at the left of the cylinder liner 60. Stud bolt holes 62 are formed in the cylinder block 23 at four corners around the cylinder liner 60 and also at upper and lower positions leftward of the chain chamber 61. Stud bolts are passed through the stud bolt holes 62 for fastening the cylinder block 23 and the cylinder head 24 to the crankcase 22. [0039]
An upper oil return passage 64 and a lower oil pressure delivery passage 63 are defined rightwardly of and adjacent to the upper and lower right stud bolt holes
62 and 62. The lower oil pressure delivery passage 63 extends somewhat in the direction of the cylinder axis and is then bent rightwardly into communication with the oil outlet opening 63a (see FIG. 6). The upper oil return passage 64 extends somewhat in the direction of the cylinder axis and is then bent rightwardly into communication with the oil inlet opening 64a. [0040]
As shown in FIG. 2, the crankcase 22 to which the cylinder block 23 is coupled is provided therein with an oil pump 66 disposed forwardly and obliquely downwardly of a crankshaft 22a, the oil pump 66 being actuatable upon rotation of the crankshaft 22a. An oil suction passage 67 extending rearwardly and obliquely downwardly from the oil pump 66 is connected to an oil strainer 68 which is disposed along the bottom of the crankcase 22. [0041]
An oil discharge passage 69 extending forwardly and obliquely upwardly from the oil pump 66 is in communication with an oil passage 70 which is defined in a mating surface of the crankcase 22 which is joined to the cylinder block 23. The oil passage 70 is branched into communication with the stud bolt holes 62 and the oil pressure delivery passage 63. The oil return passage
64 is also in conununication with an oil passage 71
defined in the crankcase 22.
[0042]
When the oil pump 66 is actuated, oil is drawn through the strainer 68 into the oil suction passage 67 and discharged into the oil discharge passage 69, from where the oil is delivered under pressure into the oil passage 70. The oil is then supplied from the oil passage 70 through the stud bolt holes 62 to a valve operating mechanism in the cylinder head 24. Part of the oil is delivered under pressure to the oil pressure delivery passage 63 and then delivered from the cylinder block 23 through the lower joint pipe 50 to the oil cooler 40 where the oil is cooled. The oil cooled by the oil cooler 40 flows through the upper joint pipe 55 and returns through the oil return passage 64 in the cylinder block 23 to the oil passage 71 in the crankcase 22. [0043]
In this manner, an oil cooling system is constructed. [0044]
Since the joint pipes 50 and 55 extending from the oil cooler 40 disposed closely and forwardly of the internal combustion engine 21 with the cylinder tilted
forwardly to a large extent are connected to the openings 63a and 64a in the side wall of the cylinder block 23, the pipes have an optimum length, not too short or too long, which provides a desired freedom of layout for the oil cooler 40, thus avoiding an increase in the manufacturing costs. [0045]
With the oil cooler 40 fixed to the downpipes 4 and 4, the oil cooler 40 can be disposed at a certain distance from the internal combustion engine 21 as a heat source, so that the oil cooler 40 is less susceptible to the heat from the internal combustion engine 21 whereby cooling efficiency of the oil cooler 40 is increased. [0046]
The oil cooler 40 is not liable to suffer vibrations of the vehicle body because it is supported by the downpipes 4 and 4 by the rubber bushings 41c, 42c and 43c. [0047]
In the present embodiment, the oil cooler is disposed forwardly of the internal combustion engine. However, the oil cooler may be disposed closely and rearwardly of the internal combustion engine. In this case also, the oil cooler may be connected to the
openings in the side wall of the cylinder block by way of pipes which have an optimum length, not too short or too long, whereby a desired freedom of layout for the oil cooler is ensured. [0048]
The cylinder head 24 can be installed and removed without the need for dismounting the pipes and other parts, whereby the lubricating oil cooling device has increased maintainability.

WE CLAIM:
1. A small-sized vehicle on which is mounted an internal combustion engine (21) including
a crankcase (22) in the rear, a cylinder block (23) attached in front of the crankcase (22), a
cylinder head (24) attached in front of the cylinder block (23), and a cylinder head cover (25)
attached in front of the cylinder head (24), wherein the cylinder block (23) has a cylinder with its
axis tilted to extend so as to be higher in the forward direction of the vehicle, wherein a heat
exchanger (40) as a lubricating oil cooling device is provided closely to the engine (21), and
wherein the cylinder block (23) has internal lubricating oil passages, characterized in that:
said cylinder block (23) has an oil inlet opening (64a) and an oil outlet opening (63a) for the internal lubricating oil passages of the cylinder block (23); a first joint pipe (50) connects said oil outlet opening (63a) of the cylinder block (23) to an oil inlet joint pipe (45) provided on the heat exchanger (40) and a second joint pipe (55) connects an oil outlet joint pipe (46) provided on the heat exchanger (40) to said oil inlet opening (64a) of the cylinder block (23).
2. The small-sized vehicle as claimed in claim 1, wherein said heat exchanger (40) is fixed to a vehicle body frame (3).
3. The small-sized vehicle as claimed in claim 1 or 2, wherein said heat exchanger (40) is fixed to downpipes (4) provided at a front part of the vehicle.
4. The small-sixed vehicle as claimed in claim 1 or 2, wherein said heat exchanger (40) is in the shape of a flat rectangular parallelepiped and has a flat surface directed in a forward direction.
5. The small-sized vehicle as claimed in claim 4, wherein said flat surface of the heat exchanger (40) is directed obliquely upward.

6. The small-sized vehicle as claimed in claim 1 or 2, wherein said oil inlet joint pipe (45) and said oil outlet joint pipe (46) are provided at a side surface of the heat exchanger (40).
7. The small-sized vehicle as claimed in claim 1 or 2, wherein said oil inlet opening (64a) and said oil outlet opening (63 a) are provided at a side surface of the cylinder block (23).
8. The small-sized vehicle as claimed in claim 1 or 2, wherein said heat exchanger (40) is disposed forwardly of the cylinder head (24).
9. The small-sized vehicle as claimed in claim 1 or 2, wherein said oil inlet opening (64a) is located at an upper portion of the cylinder block (23) and said oil outlet opening (63 a) is located at a lower portion of the cylinder block (23), wherein said oil outlet joint pipe (46) is located at an upper portion of the heat exchanger (40) and said oil inlet joint pipe (45) is located at a lower portion of the heat exchange (40), and wherein said first joint pipe (50) is located at a lower position and said second joint pipe (55) is located at an upper position.
10. The small-sized vehicle as claimed in claim 1 or 2, wherein each of said first and second joint pipes (50, 55) comprises a flexible pipe (50a or 55a) and connection pipes (50b, 50c or 55b, 55c) connected to opposite ends of the flexible pipe (50a or 55a), one (50b or 55b) of the connection pipes (50b, 50c or 55b, 55c) has a mounting bracket (51 or 56) attached to the cylinder block (23), and the other (50c or 55c) of the connection pipes (50b, 50c or 55b, 55c) has a mounting flange (52 or 57) attached to a portion of the heat exchanger (40).
11. The small-sized vehicle as claimed in claim 10, wherein said mounting bracket (51 or 56) is attached to a side surface of the cylinder block (23) with bolts (51a or 56a), and said mounting flange (52 or 57) is attached with bolts (52a or 57a) to a joint member (53 or 58) formed on said joint pipe (45 or 46) of the heat exchanger (40).